|General validity: within a calculus a formula that is satisfied by any interpretation (variable assignment with expressions for objects) is valid. See also satisfaction, satisfiability, interpretation.|
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Validity / expressiveness / modal / quantification / Stalnaker: the validity of the generalization schema - unlike the identity scheme - depends on limitations of the expressiveness of the extensional theory. If the language is richer, some new instances will be no theorems.
Ways a World may be Oxford New York 2003